قدرت قصابی

Temperature management in turbomachines is a critical factor for improving power plant efficiency and service life. Air gap clearances between combustion chamber rings assist its installation and expansion while partially modifying the inlet air path to stave off mixing in the flame tube of the combustion chamber. Changes in clearance dimensions can cause geometric asymmetry and result in asymmetric flow and temperature distribution imbalances in the combustion chambers creating hot spots at the outlet of the combustion chamber. Hence, in this paper, the effects of four clearance dimensions with four values on temperature distribution in two combustion chambers attached to the compressor have been numerically studied using Ansys Fluent 17. Taguchi method is applied for optimization and decreasing the outlet semi-circles temperature difference using Minitab software. The optimization results illustrate that the radial clearance between the flame tube and the mixing chamber is the most significant variable in controlling the air flow rate and producing symmetrical temperature distribution in the two chambers. So, one-millimeter radial clearance between two chambers leads to an increase of the temperature distribution by 15oC and 100oC in average and point mode, respectively. Also, results show that as the average clearance of the combustion chamber decreases by 5 millimeters, the point mode temperature of its corresponding outlet semi-circle decreases around 100°C.

It has been demonstrated that thermal efficiency can be improved and Nox emission can be reduced in gas turbine cycles by inlet air evaporative cooling. For this method, few studies have been performed using numerical simulations due to the complexity of the combustion and evaporation process. This study numerically and thermodynamically investigated the effect of inlet evaporative cooling on the thermal efficiency and NOx emission of a V94.2 gas turbine. The compressor and turbine are simulated using thermodynamic modeling. However, thermodynamic modeling could be able to calculate the temperature only at the inlet and outlet of devices. Analysis of evaporating cooling effect on combustion chamber temperature distributions and species distribution could be achieved by numerical method. Therefore, the combustion chamber was simulated by numerical modeling using Ansys Fluent 16. The process was simulated at four humidity ratios, including, 0, 25%, 50%, and 75%. Combustion was assumed to occur in a diffusion-type flame. The mass flow rate of fuel and air was 3.64 kg/s and 214.2 kg/s, respectively. Results show that Numerical and thermodynamic solutions have a good agreement with the empirical result. Also, it is observed that the accuracy of the numerical solution is better than the thermodynamic solution. Results indicated a 0.44% improvement in thermal efficiency and a considerable 33.5% reduction of NOx emission at the highest humidity ratio.

Many researchers have experimentally and theoretically studied fresh water productivity in solar stills. In this regard, water preheating can play a noticeable role in enhancing the productivity of solar stills. In the present study, in order to study the effect of water preheating at the inlet of desalination system, a cascade solar still is built and integrated with two different solar collector in separated modes; an evacuated solar collector and a conventional flat plate solar collector. The mentioned solar still includes an external condenser, fin, and internal and external reflectors. It is worth noting that the embedded fins in the water passage are applied to induce hot spots and increase the evaporation rate and fresh water. The experiments were performed in August 2015 and summer 2017. The results showed that the combined desalination system with conventional flat plate collector and evacuated tube collector enhace productivity %60 and %13, respectively. In addition, efficiency of solar still in combination with conventional flat plate collector and evacuated tube collector was %81.8 and %59.1, respectively. The price of produced fresh water of solar still with conventional collector obtained 0.035 $/lit and for solar still with evacuated tube collector was 0.045 $/lit.

Gas turbine inlet air is filtered in multiple steps. First, the filtration step is used for removing the big things. Then, Sand and dust are removed using the inertial sand separators. Sand separators filtration system is composed of 30 rows of the inertial sand separators on 5 floors. In this paper, one floor of the inertial sand separators filtration system of Shahid Kave power plant has been simulated using Ansys Fluent 16. A computational server with 20 processing cores and RAM of 120 GB was used to carry out the calculations. The velocity and pressure fields have been studied and the effect of density and diameter of particles on inertial sand separators efficiency are investigated. Particle diameter and density are varied between 0.1 to 100 micrometer and 500 to 2000 kg/m3 respectively. The result shows that the collection efficiency of the inertial sand separators was reduced by increasing the particle diameter. However, the collection efficiency of the inertial sand separators was improved by increasing the particle density. Also, a few particles are collected by inertial sand separators, so that collection efficiency is less than 1%. Therefore, this system is inefficient and not cost-effective and elimination of the system fans could reduce the energy consumption of the gas power plant around 360 kW.

Over the past few years, researchers were carried out a conscious effort to explore various methods of improving the thermal efficiency of power plants. It was shown that the application of a recuperator is beneficial to improve the thermal efficiency of a gas power plant. Nevertheless, a few studies were done from a thermodynamic point of view and it is safe to say that few numerical simulation studies were performed using computational fluid dynamics. Therefore, in this study, the effect of using a recuperator was investigated to increase the temperature of the combustion chamber inlet air at four different temperatures (633, 643, 663 and 673 K) and to enhance the overall thermal efficiency. Furthermore, the effect of this approach on the emission of pollutants was explored. For this purpose, the compressor and turbine were numerically simulated using a developed MATLAB code while the combustion chamber of the gas power plant was simulated for various pre-heated temperatures in a thermodynamic analysis by ANSYS Fluent 16. The results indicated that in the case of the highest increase in the inlet air temperature to the combustion chamber (50°C) compared to the basic state (without recuperation), the thermal efficiency of the power plant and emission of nitrogen oxides were increased by 1.46% and by 44.17%, respectively.

The current empirical study was conducted to investigate the wall neighborhood impact on the two-dimensional flow structure and heat transfer enhancement behind a square cylinder. The low- velocity open-circle wind tunnel was used to carry out the study tests considering the cylinder diameter (D)-based Reynolds number (ReD) of 5130. The selected items to compare were different gap height (G/D= 0.0, 0.1, 0.2 and 0.8). The flow field was measured using particle image velocimetry (PIV) with high image-density camera. The PIV-derived time-averaged quantities, including the streamline pattern, streamwise velocity fluctuation intensity, and reverse-flow intermittency, were examined for the flow past the square cylinder. The measurements of PIV were decomposed with the help of proper orthogonal decomposition (POD) approach that provides a proper view of the POD modes. To obtain the value of the heat transfer enhancement behind the square cylinder, the full-field temperature distributions of flat plate were measured through the temperature-sensitive paint (TSP) technique. Results showed that the maximum heat transfer enhancement was obtained at G/D=0.2 due to the high unstable flow near the wall.